Centrifugal fans



Nov. 15, 1966 J. E. MCDONALD CEN'IRIFUGAL FANS 2 Sheets-Sheet 1 Filed Dec. 7, 1964 INVENTOR John E, Mc Done? /o BY W 0 ,VM

1966 J. E. M DONALD CENTRIFUGAL FANS 2 Sheets-Sheet 2 Filed Dec. 7, 1964 INVENTOR. (John E. Me Dond/c/ BYW 7 W W United States Patent Ofiice 3,285,501 Patented Nov. 15, 1966 3,285,501 CENTRIFUGAL FANS John E. McDonald, 67 Colbert Road, Newton, Mass. Filed Dec. 7, 1964, Ser. No. 416,216 12. Claims. (Cl. 230127) This invention relates to centrifugal tans, and has as an object to improve the inlet passages of such fans.

Conventional centrifugal fans have converging casing walls forming axial inlet passages to their wheels, and their wheels have side plates with straight, radially extending outer portions joined to inner portions which are curved to attempt to change the direction of the air entering the wheels from axial to radial. Experience has shown that the air passing through such a wheel does not follow closely the shape of its side plate, but breaks away from the latter, resulting in the fan blades being only partially loaded.

This invention produces an annular ring of spinning air around the inlet of a fan wheel, with the air spinning in a direction to cause the air entering the wheel to change from an axial to a radial direction. In one embodiment of this invention this is accomplished by [forming an inner portion of a side plate of a fan wheel as a portion of an annular ring, and by forming an adjacent portion of a fixed casing wall as a portion of an annular ring extending partially around the ring shaped portion of the side plate. High pressure air from within the casing of the fan is directed between the two ring shaped portions, and is caused by their curvature to spin around the inlet of the fan wheel, and by induction to cause the direction of the air entering the fan wheel to change trom axial to radial.

Another object of this invention is to use air spinning around the axial inlet of a wheel of a centrifugal fan, to cause the direction of the air entering the fan wheel to change from axial to radial.

This invention will now be described with reference to the annexed drawings, of which:

FIG. 1 is a side view, in section, of a centrifugal fan embodying this invention;

FIG. 2 is an end view of the fan of FIG. 1, looking at its inlet end; the scale being reduced;

FIG. 3 is an enlarged, fragmentary view, in section of the upper portion of FIG. 1, and shows by arrows the directions of the spinning air, and the air entering the fan wheel;

FIG. 4 is a modification of FIG. 3, with the arrows omitted;

FIG. 5 is another modification of FIG. 3, with the arrows omitted;

FIG. 6 is still another modification of FIG. 3, with the arrows omitted, and

FIG. 7 is a fragmentary end view of the spin removing vanes of FIG. 4.

Referring first to FIGS. 1-3, a conventional scrollshaped casing 10 has the usual axial inlet 11 and tangential outlet 12. The casing 10 has a wall 13 converging inwardly from the inlet 11, and forming a converging, axial inlet passage 14. Inner end 15 of the wall 13 has joined thereto a wall portion 16 formed as a portion of an annular ring, and which has joined thereto, radially outwardly of the inner end 15 of the wall 13, a cylindrical wall portion 17. A fan wheel 18 has a back plate 19 attached to a shaft 20, the usual hub not being shown, and has a side plate 21. The side plate 21 has a radially extending, outer portion 212, and has an inner portion 23 formed as a portion of an annular ring, and which extends inwardly of the cylindrical wall portion 17, and the axially outer end of which is in a vertical plane containing the inner end 15 of the wall 13. An annular passage 25 is formed between the rin -shaped side plate portion 23 and the cylindrical wall 17, and supplies high pressure air from within the casing 10 tangentially into the space bounded by the ring-shaped wall portion 16. The wheel 21 has conventional fan blades 26, and has an axial inlet 27 axially aligned with noses 28 of the blades 26, and the inner end of the straight portion 22 of the side plate 21.

In the operation of FIGS. l-3, the high pressure air within the casing 10 flows through the annular passage 25, and is caused by the curved wall portion 16 to spin as shown by the arrows of FIG. 3, around the inlet 27 of the wheel 21. Approximately one fourth of the boundary layer of the spinning air is in contact with the boundary layer of the air leaving the passage 14, and the latter air is caused by induction to turn from an axial to a radial direction, the boundary layer of the spinning air passing into the inlet 27 of the fan wheel with the main air stream.

Under certain conditions, the spinning air may tend to rotate bodily in the same direction as the rotation of the fan wheel. To prevent this, the spin removing vanes 30 shown by FIGS. 4 and 7, extend axially inwardly from the axially inner surface of the ring-shaped wall 16 into the path of spinning air rotating in the direction that the fan wheel does. The vanes 30 do not interfere with the air spinning in an annulus, and may be shaped to increase such spin.

In a high pressure fan, the velocity of the spinning air at the center of its vortex may increase to such a high velocity that shock waves and/ or noise may be produced. To prevent this, an annular core 31 in the form of a toroid, as shown by FIG. 5, can be placed in the center of the vortex to fill in its central portion. The core 31 is supported from the curved wall portion 16 by spin removing vanes 32, similar to, but smaller, than the vanes 30 shown by FIGS. 4 and 7.

In the embodiments of the invention shown by FIGS. 1-5, the curved wall portions 16 and the side plate portions 23 are circular in section. FIG. 6 shows a modification in which a side plate portion 23a corresponding to theside plate portions 23 of FIGS. 1-5, is straight and is parallel to cylindrical wall portion 17a extending therearound, and which corresponds to the wall portions 17 of FIGS. 1-5, with a tangential, annular passage 25a corresponding to the passages 25 of FIGS. 1-5, between the side plate portion 23a and wall 1721. Wall portion 16a corresponding to the wall portions 16 of FIGS. 1-5, has, in section, a smaller arc than the wall portions 16; is not joined to the axially inner end of wall 13a corresponding to the walls 13 of FIGS. 1-5, and its radially inner end is joined to a wall portion 34 spaced radially outward from and parallel to the wall 13a, with a tangential, annular passage 35 formed between the wall 13a and the wall portion 34. Inner end portion 36 of the wall 13a is turned outwardly towards the side plate portion 23a. The wall portion 34 is supported from the wall 13a by spaced apart struts 40.

The operation of FIG. 6 is smiliar to that of FIGS. 1-3 with tthe exception that additional high pressure air from within the casing fiows through the passage 35 tangentially into the space bounded by the wall portion 16a and the inner end portion of the wall 13a. The outwardly turned inner end portion 36 of the wall 13a greatly increases the spinning.

The inlets of the fan wheels of FIGS. 1-6 are circular and axial as is conventional. The inner ends of the walls 13 of FIGS. 1-5, and the inner end of the wall 13a of FIG. 6, are in circles having smaller diameters than the inlets of their respective fan wheels, such circles being in planes normal to the axes of the respective wheels.

The wall portions 16 and the inner end portions of the walls 13 of FIGS. 1-5, form generally parti-toroidal wall means extending partially around circular axes in planes normal to the axes of the respective fan wheels, such wall ,which the wall 16 and the inner portion of the Wall 13 of FIG. 5 extend.

What is claimed, is:

1. A centrifugal fan comprising a casing; a fan Wheel supported for rotation within said casing, said wheel having a circular axial inlet, and having a side plate around said inlet; said casing having an inlet concentric with said inlet, and having a relatively long annular wall extending from said inlet of said casing towards said inlet of said Wheel, said wall having an axially inner end in a circle concentric with said inlets and in a plane normal to the axis of said wheel, said end being spaced axially outward- -ly from said inlet of said wheel; generally parti-toroidal, fixed Wall means extending partially around a circular axis, and having a radially inner portion formed by a relatively short portion of said wall extending from said end towards said inlet of said casing, said circular axis having a smaller diameter than that of said wheel, said Wall means having a radially outer portion with an axially inner end closely adjacent to said side plate, said wall means having a curved, in section, intermediate portion extending around said inner portion and bulging towards but terminating short of said inlet of said casing, said Wall means being open between said inner end and said inlet of said wheel; and means for supplying high pressure air from the interior of said casing tangentially into the space bounded by said wall means, said wall means being shaped to cause the high pressure supplied into said space to spin around said circular axis.

2. A centrifugal fan as claimed in claim 1 in which a plurality of spin removing vanes are spaced apart in said space and have outer edges in contact with the inner surface of said wall means.

3. A centrifugal fan as claimed in claim 1 in which a toroid having a diameter, in section, substantially smaller than the diameter, in section, of said wall means is located on said circular axis.

4. A centrifugal fan comprising a casing; a fan wheel supported for rotation within said casing, said wheel hav- .wall means extending around a circular axis in a plane normal to the axis of said Wheel, said circular axis being spaced axially outwardly from said side plate, having a smaller diameter than that of said Wheel, and having a larger diameter than that of said circle, said wall means including a relatively short portion of said wall extending from said end towards said inlet of said casing, said wall means being open between said end and said side plate edge; and means for supplying high pressure air from within said casing tangentially into the space bounded by said Wall means, said wall means being shaped to cause the high pressure air supplied into said space to spin around said circular axis.

5. A centrifugal fan as claimed in claim 4 in which a plurality of spin removing vanes are spaced apart in said space and have outer edges in contact with the inner surface of said wall means.

6. A centrifugal fan as claimed in claim 4 in which a toroid having a diameter, in section, substantially smaller than the diameter, in section, of said wall means is located on said circular axis.

7. A centrifugal fan comprising a casing; a fan wheel supported for rotation within said casing, said wheel having a circular axial inlet, and having a side plate around said inlet; said casing having an inlet concentric with said inlet, and having a relatively long annular wall extending from said inlet of said casing towards said inlet of said Wheel, said wall having an axially inner end in a circle concentric with said inlets, said end being spaced axially outwardly from said inlet of said Wheel; generally partitoroidal, fixed wall means extending partially around a circular axis in a plane normal to the axis of said Wheel, said circular axis being spaced axially outwardly from said side plate, having a smaller diameter than that of said wheel, and having a larger diameter than that of said circle, said Wall means having a radially inner portion formed by a relatively short portion of said wall extending from said end towards said inlet of said casing, said wall means having a radially outer portion with an end closely adjacent to said side plate, said Wall means having an intermediate portion curved, in section, extending around said inner portion and bulging towards but terminating short of said inlet of said casing, said wallmeans being open between said inner end and said inlet of said wheel; said side plate having means extending axially outwardly and spaced radially inwardly of said end of said outer portion and forming with said end of said outer portion a passage for supplying high pressure air from within said casing tangentially into the space bounded by said wall means, said wall means being shaped to cause the high-pressure air supplied into said space to spin around said circular axis.

8. A centrifugal fan as claimed in claim 7 in which a plurality of spin removing vanes are spaced apart in said space and have outer ends in contact with the inner surface of said Wall means.

9. A centrifugal fan as claimed in claim 7 in which a toroid having a diameter, in section, substantially smaller than the diameter, in section, of said wall means is located on said circular axis.

10. A centrifugal fan as claimed in claim 1 in which said inner end of said wall is turned outwardly towards said side plate.

11. A centrifugal fan as claimed in claim 4 in which said inner end of said wall is turned outwardly towards said side plate.

12. A centrifugal fan as claimed in claim 7 in which said iriner end of said wall is turned outwardly towards said side p ate.

References Cited by the Examiner UNITED STATES PATENTS 820,779 5/1906 Guy 230-122 971,850 10/1910 Krogh 103-l03 1,787,656 1/1931 Anderson 230-127 2,798,658 7/1957 McDonald 230127 3,070,025 12/ 1962 Cliborn 103-103 FOREIGN PATENTS 375,065 6/1921 Germany.

21,286 of 1901 Great Britain. 858,808 1/ 1961 Great Britain.

MARK NEWMAN, Primary Examiner. HENRY F. RADUAZO, Examiner. 

1. A CENTRIFUGAL FAN COMPRISING A CASING; A FAN WHEEL SUPPORTED FOR ROTATION WITHIN SAID CASING, SAID WHEEL HAVING A CIRCULAR AXIAL INLET, AND HAVING A SIDE PLATE AROUND SAID INLET; SAID CASING HAVING AN INLET CONCENTRIC WITH SAID INLET, AND HAVING A RELATIVELY LONG ANNULAR WALL EXTENDING FROM SAID INLET OF SAID CASING TOWARDS SAID INLET OF SAID WHEEL, SAID WALL HAVING AN AXIALLY INNER END IN A CIRCLE CONCENTRIC WITH SAID INLETS AND IN A PLANE NORMAL TO THE AXIS OF SAID WHEEL, SAID END BEING SPACED AXIALLY OUTWARDLY FROM SAID INLET OF SAID WHEEL; GENERALLY PARTI-TOROIDAL, FIXED WALL MEANS EXTENDING PARTIALLY AROUND A CIRCULAR AXIS, AND HAVING A RADIALLY INNER PORTION FORMED BY A RELATIVELY SHORT PORTION OF SAID WALL EXTENDING FROM SAID END TOWARDS SAID INLET OF SAID CASING, SAID CIRCULAR AXIS HAVING A SMALLER DIAMETER THAN THAT OF SAID WHEEL, SAID WALL MEANS HAVING A RADIALLY OUTER PORTION WITH AN AXIALLY INNER END CLOSELY ADJACENT TO SAID SIDE PLATE, SAID WALL MEANS HAVING A CURVED, IN SECTION, INTERMEDIATE PORTION 